Conventionally, a push-button switch has a key top which is pressed by fingers to be operated, and supported by an elastic support body such as a spring. The key top is pressed down against a supporting force of the elastic support body, so that a movable contact integrally formed with the key top comes into contact with a fixed contact, so that an electrical circuit is energized conductive.
Recently, a mobile electronic equipment is provided with many switch mechanisms for input of operations. As shown in FIG. 7A, the switch mechanism includes the push-button switch in which a button 101 made of an elastic material such as a silicon rubber is integrally provided with a buckling wall 103 in its lower part, and is elastically supported by the buckling wall 103.
In this case, the button 101 protrudes outward through a through-hole 8 made in a cover body 109, providing a predetermined clearance between the through-hole 108 and the periphery of the button 101. When the button 101 is pressed down from directly overhead, the button 101 moves along its axis, and a movable contact 116 comes in contact with fixed contacts 105, 106 securely (see FIG. 7B). However, when a user presses an edge, or a cover, of the button 101, the button 101 moves inclining as shown in FIG. 7C, and the movable contact 116 touches only a part of the fixed contacts 105, 106. This results in a state of poor contact. When the button 101 is pressed inclining, the outer edge of the button 101 comes into contact with an inner circumference of the through-hole 8 in the cover body 9, thereby interfering smooth returning of the button 101.
To cope with the above problems, Japanese examined utility model publication No. S63(1988)-43715 discloses a push-button switch arranged as follows: a turning support part of which a bottom end is always in contact with a board, or an upper end is with the bottom end of the button, is provided on the underside of the button in order to prevent one of four faces of a returning elastic body formed along a perimeter of a button from becoming deformed by the operating force on the button. When operated, the button is inclined with its one side supported on the turning support body.
However, the push-button switch of the '715 publication has several problems because the push-button switch is inclined with its one side supported as stated above. Specifically, when a user presses the top face of the button at the side opposite to the turning support part, a pulling force of the button on the returning elastic body is generated on the turning support part side. Because of the force, the user would need to press the button with the stronger force, and feel worse click touch. The returning elastic body would be broken with continuous pressing the button.